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| Titel |
Distinct effects of water use efficiency increase on growth in Scots pine
and sessile oak in the Mediterranean Basin |
| VerfasserIn |
Elisabet Martínez-Sancho, Isabel Dorado-Liñán, Emilia Gutiérrez-Merino, Michael Matiu, Ingo Heinrich, Gerhard Helle, Annette Menzel |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149106
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| Publikation (Nr.) |
 EGU/EGU2017-13426.pdf |
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| Zusammenfassung |
| Drought is one of the main drivers of species distribution in the Mediterranean Basin, which
will be exacerbated by climate change. The increase of atmospheric CO2 concentrations (Ca)
has been related to enhanced tree growth and intrinsic water use efficiency (iWUE).
However, in the Mediterranean Basin this ‘fertilizing’ effect should compensate
the potential drought-induced growth reduction to maintain forest productivity at
a comparable level. This is particularly relevant for temperate species reaching
their southern distribution limits and/or the limits of their climatic niche in this
region.
We investigated tree growth and physiological responses of Scots pine (Pinus sylvestris
L.) and sessile oak (Quercus petraea (Matt.) Liebl.) stands located at their southern
distribution limits using annually resolved tree-ring width and δ13C chronologies for the
period 1960-2012. The selected stands were sampled in Spain, France, Italy, Slovenia,
Bulgaria, and Romania. Wood cores were extracted at each site and tree-ring width and δ13C
were measured. Basal area increment (BAI) was calculated as a surrogate of secondary
growth and 13C discrimination (Δ), leaf intercellular CO2 concentration (Ci) and
iWUE were estimated from δ13C values. The temporal trends of BAI, Δ, Ci and
iWUE, as well as in climatic variables (i.e. temperature, precipitation and potential
evapotranspiration derived from CRU TS3.23 dataset) were calculated per site for the study
period.
Our specific objectives were (i) to test if rising atmospheric CO2 concentrations and
changes in climate may have induced shifts in tree growth and ecophysiological proxies; (ii)
to determine whether and how changes in iWUE are related to radial growth rates; and (iii) to
assess site-specific physiological adjustments to increased atmospheric CO2 concentrations
over the studied period.
Preliminary results showed a generalized increase in Ci, and consequently in iWUE, at all
study sites. Scots pine stands displayed a significant decreased in BAI likely induced by
summer droughts, leading to a negative relationship between iWUE and BAI. In addition,
most of the pine stands kept a constant Ci/Ca over the study period. Sessile oak stands
displayed positive growth trends over the study period and correlations of BAI with
summer drought were lower and scarcer. Oak stands located in the eastern part of the
Mediterranean Basin displayed a positive relationship between iWUE and BAI whereas this
relationship was negative for the western stands. The Ci from most of the oak sites
followed the Ca trends over time. However, oak sites with higher water availability
displayed positive trends in the Ci/Ca ratio indicating a weak stomatal response. |
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